Plan to watch how materials bond together at atomic level

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OAK RIDGE, Tenn. — Oak Ridge National Laboratory researchers are peering into the atomic world with record clarity, developing an electron microscope image that can distinguish the individual, dumbbell-shaped atoms of silicon in a crystal.

"Every time you see something more clearly you learn some secrets," said Stephen Pennycook, who heads the lab's electron microscopy group.

Pennycook and colleagues write in a Sept. 17 article in the journal Science that they have achieved an image resolution at 0.6 angstrom, breaking the previous record of 0.7 angstrom that the lab set earlier this year.

An angstrom is the smallest wavelength of light. One angstrom is about 500,000 times smaller than the thickness of a human hair. Most atoms are about 1 angstrom in diameter.

"We are crossing that threshold where we can really see atoms clearly for the first time ever," Pennycook said.

He said being able to see how materials bond together at an atomic level could be of great benefit to the semiconductor industry, chemistry and in the development of new materials.

The lab produced an image of silicon atoms appearing as red dumbbell-shaped objects in columns that were a mere 0.78 angstrom apart. "This is the first unequivocal proof that we're getting subangstrom resolution," Pennycook said.

The Department of Energy team used a 300-kilovolt state-of-the-art electron microscope aided by new computerized imaging technology called aberration correction developed by Nion Co. of Kirkland, Wash.

Pennycook compared the resolution correction technology to being able to focus 50 lenses simultaneously.

"That is what makes it really quite a historic achievement because it has been attempted for the last 50 years actually, and only in the last few years has it really proved feasible," he said.

Five years ago the Oak Ridge lab set a world record with a resolution at 1.3 angstrom without the aberration technology. With the technology, it set the previous record at 0.7 angstrom earlier this year. Researchers said the next frontier will be seeing atoms in three dimensions.

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